Interpretive Summary: Poultry litter is typically reused over successive flocks. Concerns over pathogen transmission from flock to flock have precipitated a number of methods to sanitize litter before new flocks are placed. Windrowing the litter after decaking and allowing microbes to heat the litter, similar to a composting process, has been widely adopted. The windrowing process mixes litter from different depths and the objective of this study was to determine the bacterial composition of litter at those different depths. Results indicate that there are significantly more anaerobic and coliform bacteria in the upper three inches of litter when compared to greater depths.

Technical Abstract:
A common practice in the commercial broiler industry is to reuse litter over multiple broiler flocks. Morbidity, mortality, and condemnation have been attributed to pathogenic bacteria which reside in used litter. Information that describes how bacteria are distributed throughout the litter bed is sparse. Therefore, the goal of this project was to investigate the distribution of bacteria at three different depths of litter. Litter samples were collected from three commercial broiler houses on three different farms. Four samples from each house were collected using clear PVC pipes which were driven through the litter bed to the clay floor. Each pipe was transported up-right to the lab, where they were cut into three sections (top, middle, and bottom) exposing the litter for processing. Litter from each section was serially diluted in peptone and streaked onto either tryptic soy agar or Levin eosin methylene blue agar plates. Plates were incubated under the appropriate atmospheric condition for 24 hours at 37oC. After 24 hours, plates were counted for total aerobes, anaerobes, and coliforms. Results of this study indicate a significant difference (P<0.05) in bacterial counts between the different sections of the litter. The middle and bottom sections had significantly lower anaerobic, and coliform counts compared to the bacterial counts in the top sections. In conclusion, the results suggest that the middle and bottom section of litter provide a less favorable environment for bacterial growth than the top section.